To provide a data controller capable of surely preventing illegal editing or the like from an optional user from being performed to data and improving the reliability of the data.

In preparing or editing the object of a graphic or a character or the like corresponding to the instruction of a user from a keyboard 107 or the like and preserving it as the data in an FD 105 or the like, additional information (individual information relating to the user who prepares and edits the object and the preparation date and time, etc.), relating to the data is buried in the data by an electronic watermark method and preserved. In the case that data output by a printer 109 or the like is instructed, the propriety of the data output is judged by the additional information in the data of an output object.